On 27 Oct 2006 03:33:23 -0700, "OH1GTF" wrote:

Hi fellows!

I'm building a software defined radio that is mostly based on the
"Software Defined Radios For The Masses" -articles and are at the point
of designing the DDS board. I have two units of AD9954 DDS chips and
my idea was to use them parallel, other one with 90 degree phase shift
to generate the quadrature signal. This is my first time with DDS, so
understanding the control seem to be a little bit difficult for a first
timer.

Two questions to start with:

1. I suppose for proper control I need four pins connected from the DDS
to the computer (through buffers) I/O update, SDIO, SCLK and Reset, am
I correct?

2. Do I have to drive two SDIO serial signals separately for each DDS
chip from computer so, that I can define the phase shift for the other
DDS (while other one has no phase shift, obivously) ? This came to my
mind since the chips don't have any addresses to indentify them.

Thanks a lot!!!

73 de Janne, OH1GTF

I dying to know how you make out. Here's why:
I have some DDSs, AD9911, I can't get to do anything. They have the
same I/O lines: I/O update, Reset, SDIOs and SCLK. I used a BasicStamp
to control it: Reset high, SCLK it, send in data on SDIO line, then
pulse IO_Update, nothing. Used a 10 Mhz system clock from an HP
generator. Though my one problem is the AD9911 I/Os are 3.3 volts, so
I used resistor divider on the uController outputs to the AD9911 to
drop the level, maybe that has something to do with it, I'm waiting
for 3.3 - 5 v level shiftrs from Maxim to come, MAX3371.